In poultry hatcheries and other egg processing facilities, eggs are handled and processed in large numbers. The term “processing” includes, but is not limited to, treating live eggs with medications, nutrients, hormones and/or other beneficial substances while the embryos are still in the egg (i.e., in ovo). In ovo injections of various substances into avian eggs have been employed to decrease post-hatch morbidity and mortality rates, increase the potential growth rates or eventual size of the resulting bird, and even to influence the gender determination of the embryo. Injection of vaccines into live eggs has been effectively employed to immunize birds in ovo.
Referring now to FIG. 1, an avian egg 10 is illustrated. The illustrated egg 10 includes a shell 12, an outer shell membrane 14, an inner shell membrane 16, and an air cell 18 at the blunt end of the egg 10 between the inner and outer shell membranes 14, 16. The illustrated egg 10 also includes a yolk 20 and blastoderm 22 surrounded by inner thin albumen 24a, outer thick albumen 24b, and outer thin albumen 24c. The blastoderm 22 is a cellular disc several cells deep that sits atop a “subgerminal cavity” 26 (FIG. 2). The edges of the blastoderm disc 22 are attached to the yolk 20.
Currently, to produce chimeric chickens, cells are injected into the subgerminal cavity of an avian egg by puncturing the blastoderm with a needle and delivering the cells into the subgerminal cavity. However, because the subgerminal cavity within an avian egg is very small, accurate delivery of cells into the subgerminal cavity can be difficult. Moreover, an operator may have little or no control over the depth that a needle is extended into the subgerminal cavity. In addition, the size and depth of a subgerminal cavity can vary from egg to egg. As such, injection of cells into the subgerminal cavity is typically referred to as “blind injection” because it may not be possible to know whether cells have actually been inserted within the subgerminal cavity of an egg until a chick hatches and can be tested for chimerism. Accordingly, there is a need in the art for improved methods of reliably and accurately positioning devices within the subgerminal cavity of avian eggs.